Dorsal transscaphoid-transtriquetral perilunate dislocation in pseudarthrosis of the scaphoid.

A patient reported that he sustained a minor fall on the outstretched hand in hyperextension, pronation, and in ulnar deviation. Initial radiographs suggested dorsal transscaphoid-transtriquetral perilunate dislocation. Traditionally, however, this injury is the result of a high-energy impact. A CT scan obtained after closed reduction of the dislocation revealed not only a fresh fracture of the triquetrum but also two corticalized fragments of the scaphoid. A former major fall on this hand and a normal scaphoid of the other hand made pseudarthrosis more likely than scaphoid bipartition. Arthrography revealed intact lunotriquetral and scapholunate ligaments, precluding the possibility of preexisting ligamentous instability. Pseudarthrosis of the scaphoid with a loss of scaphoid function as a mechanical tie-rod of the carpus is most likely responsible for this complex injury. This is the first clinical study that shows that single scaphoid discontinuity without preexisting ligamentous carpal instability may lead to complex perilunar dislocation in minor trauma.